The Association Between Ambient PM2.5 Exposure and Anemia Outcomes Among Children Under Five Years of Age in India

Background: Anemia is highly prevalent in India, especially in children. Exposure to ambient fine particulate matter (PM2.5) is a potential risk factor for anemia via. systemic inflammation. Using health data from the National Family and Health Survey 2015-2016, we examined the association between ambient PM2.5 exposure and anemia in children under five across India through district-level ecological and individual-level analyses. Methods: The ecological analysis assessed average hemoglobin levels and anemia prevalence (hemoglobin<11g/dL considered anemic) by district using multiple linear regression models. The individual-level analysis assessed average individual hemoglobin level and anemia status (yes/no) using generalized linear mixed models to account for clustering by district. Ambient PM2.5 exposure data were derived from the Multiangle Imaging SpectroRadiometer (MISR) level 2 aerosol optical depth (AOD) data and averaged from birth date to date of interview. Results: The district-level ecological analysis found that, for every 10 mu g m(-3) increase in ambient PM2.5 exposure, average anemia prevalence increased by 1.90% (95% CI=1.43, 2.36) and average hemoglobin decreased by 0.07g/dL (95% CI=0.09, 0.05). At the individual level, for every 10 mu g m(-3) increase in ambient PM2.5 exposure, average hemoglobin decreased by 0.14g/dL (95% CI=0.12, 0.16). The odds ratio associated with a 10-mu g m(-3) increase in ambient PM2.5 exposure was 1.09 (95% CI=1.06, 1.11). There was evidence of effect modification by wealth index, maternal anemia status, and child BMI. Conclusion: Our results suggest that ambient PM2.5 exposure could be linked to anemia in Indian children, although additional research on the underlying biologic mechanisms is needed. Future studies on this association should specifically consider interactions with dietary iron deficiency, maternal anemia status, and child BMI.